Extract mkFlake to own file - get flake-parts from npins (#447)

The goal is to contain the “`mkFlake` hack” to a file that we can heavily document but otherwise ignore. This also will allow me to reuse it in the “flake under test” of the deployment tests.

Reviewed-on: Fediversity/Fediversity#447
Reviewed-by: Valentin Gagarin <valentin.gagarin@tweag.io>
Reviewed-by: kiara Grouwstra <kiara@procolix.eu>
Co-authored-by: Nicolas “Niols” Jeannerod <nicolas.jeannerod@moduscreate.com>
Co-committed-by: Nicolas “Niols” Jeannerod <nicolas.jeannerod@moduscreate.com>

deployment/check/common/deployerNode.nix

@@ -54,11 +54,11 @@ in
 
     system.extraDependencies =
       [
-        inputs.flake-parts
-        inputs.flake-parts.inputs.nixpkgs-lib
         inputs.nixops4
         inputs.nixops4-nixos
         inputs.nixpkgs
+
+        sources.flake-parts
         sources.flake-inputs
 
         pkgs.stdenv

deployment/check/common/nixosTest.nix

@@ -138,7 +138,6 @@ in
         deployer.succeed("""
           nix flake lock --extra-experimental-features 'flakes nix-command' \
             --offline -v \
-            --override-input flake-parts ${inputs.flake-parts} \
             --override-input nixops4 ${inputs.nixops4.packages.${system}.flake-in-a-bottle} \
             \
             --override-input nixops4-nixos ${inputs.nixops4-nixos} \
@@ -151,7 +150,6 @@ in
             } \
             --override-input nixops4-nixos/git-hooks-nix ${emptyFlake} \
             \
-            --override-input nixpkgs ${inputs.nixpkgs} \
             --override-input git-hooks ${inputs.git-hooks} \
             ;
         """)

flake.lock

@@ -143,24 +143,6 @@
       }
     },
     "flake-parts_3": {
-      "inputs": {
-        "nixpkgs-lib": "nixpkgs-lib_3"
-      },
-      "locked": {
-        "lastModified": 1738453229,
-        "narHash": "sha256-7H9XgNiGLKN1G1CgRh0vUL4AheZSYzPm+zmZ7vxbJdo=",
-        "owner": "hercules-ci",
-        "repo": "flake-parts",
-        "rev": "32ea77a06711b758da0ad9bd6a844c5740a87abd",
-        "type": "github"
-      },
-      "original": {
-        "owner": "hercules-ci",
-        "repo": "flake-parts",
-        "type": "github"
-      }
-    },
-    "flake-parts_4": {
       "inputs": {
         "nixpkgs-lib": [
           "nixops4-nixos",
@@ -342,7 +324,7 @@
     "nix": {
       "inputs": {
         "flake-compat": "flake-compat_3",
-        "flake-parts": "flake-parts_4",
+        "flake-parts": "flake-parts_3",
         "git-hooks-nix": "git-hooks-nix_2",
         "nixfmt": "nixfmt",
         "nixpkgs": [
@@ -416,7 +398,7 @@
     },
     "nixops4": {
       "inputs": {
-        "flake-parts": "flake-parts_3",
+        "flake-parts": "flake-parts_2",
         "nix": "nix",
         "nix-cargo-integration": "nix-cargo-integration",
         "nixpkgs": "nixpkgs_3",
@@ -438,7 +420,7 @@
     },
     "nixops4-nixos": {
       "inputs": {
-        "flake-parts": "flake-parts_2",
+        "flake-parts": "flake-parts",
         "git-hooks-nix": "git-hooks-nix",
         "nixops4": "nixops4",
         "nixops4-nixos": [
@@ -520,18 +502,6 @@
         "url": "https://github.com/NixOS/nixpkgs/archive/072a6db25e947df2f31aab9eccd0ab75d5b2da11.tar.gz"
       }
     },
-    "nixpkgs-lib_3": {
-      "locked": {
-        "lastModified": 1738452942,
-        "narHash": "sha256-vJzFZGaCpnmo7I6i416HaBLpC+hvcURh/BQwROcGIp8=",
-        "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/072a6db25e947df2f31aab9eccd0ab75d5b2da11.tar.gz"
-      },
-      "original": {
-        "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/072a6db25e947df2f31aab9eccd0ab75d5b2da11.tar.gz"
-      }
-    },
     "nixpkgs-old": {
       "locked": {
         "lastModified": 1735563628,
@@ -664,7 +634,6 @@
     },
     "root": {
       "inputs": {
-        "flake-parts": "flake-parts",
         "git-hooks": "git-hooks",
         "nixops4": [
           "nixops4-nixos",

flake.nix

@@ -1,83 +1,48 @@
 {
   inputs = {
-    flake-parts.url = "github:hercules-ci/flake-parts";
     git-hooks.url = "github:cachix/git-hooks.nix";
     nixops4.follows = "nixops4-nixos/nixops4";
     nixops4-nixos.url = "github:nixops4/nixops4-nixos";
   };
 
   outputs =
-    inputs@{ self, flake-parts, ... }:
+    inputs:
-    let
+    import ./mkFlake.nix inputs (
-      sources = import ./npins;
+      { inputs, ... }:
-      inherit (import sources.flake-inputs) import-flake;
-      inherit (sources) git-hooks;
-      # XXX(@fricklerhandwerk): this atrocity is required to splice in a foreign Nixpkgs via flake-parts
-      # XXX - this is just importing a flake
-      nixpkgs = import-flake { src = sources.nixpkgs; };
-      # XXX - this overrides the inputs attached to `self`
-      inputs' = self.inputs // {
-        nixpkgs = nixpkgs;
-      };
-      self' = self // {
-        inputs = inputs';
-      };
-    in
-    # XXX - finally we override the overall set of `inputs` -- we need both:
-    #       `flake-parts obtains `nixpkgs` from `self.inputs` and not from `inputs`.
-    flake-parts.lib.mkFlake
       {
-        inputs = inputs // {
+        imports = [
-          inherit nixpkgs;
+          "${inputs.git-hooks}/flake-module.nix"
-        };
+          inputs.nixops4.modules.flake.default
-        self = self';
+
-        specialArgs = {
+          ./deployment/flake-part.nix
-          inherit sources;
+          ./infra/flake-part.nix
-        };
+          ./keys/flake-part.nix
+          ./secrets/flake-part.nix
+        ];
+
+        perSystem =
+          {
+            pkgs,
+            lib,
+            ...
+          }:
+          {
+            formatter = pkgs.nixfmt-rfc-style;
+
+            pre-commit.settings.hooks =
+              let
+                ## Add a directory here if pre-commit hooks shouldn't apply to it.
+                optout = [ "npins" ];
+                excludes = map (dir: "^${dir}/") optout;
+                addExcludes = lib.mapAttrs (_: c: c // { inherit excludes; });
+              in
+              addExcludes {
+                nixfmt-rfc-style.enable = true;
+                deadnix.enable = true;
+                trim-trailing-whitespace.enable = true;
+                shellcheck.enable = true;
+              };
+          };
       }
-      (
+    );
-        { inputs, ... }:
-        {
-          systems = [
-            "x86_64-linux"
-            "aarch64-linux"
-            "x86_64-darwin"
-            "aarch64-darwin"
-          ];
-
-          imports = [
-            "${git-hooks}/flake-module.nix"
-            inputs.nixops4.modules.flake.default
-
-            ./deployment/flake-part.nix
-            ./infra/flake-part.nix
-            ./keys/flake-part.nix
-            ./secrets/flake-part.nix
-          ];
-
-          perSystem =
-            {
-              pkgs,
-              lib,
-              ...
-            }:
-            {
-              formatter = pkgs.nixfmt-rfc-style;
-
-              pre-commit.settings.hooks =
-                let
-                  ## Add a directory here if pre-commit hooks shouldn't apply to it.
-                  optout = [ "npins" ];
-                  excludes = map (dir: "^${dir}/") optout;
-                  addExcludes = lib.mapAttrs (_: c: c // { inherit excludes; });
-                in
-                addExcludes {
-                  nixfmt-rfc-style.enable = true;
-                  deadnix.enable = true;
-                  trim-trailing-whitespace.enable = true;
-                  shellcheck.enable = true;
-                };
-            };
-        }
-      );
 }

mkFlake.nix

@@ -0,0 +1,47 @@
+## This file contains a tweak of flake-parts's `mkFlake` function to splice in
+## sources taken from npins.
+
+inputs@{ self, ... }:
+
+let
+  sources = import ./npins;
+  inherit (import sources.flake-inputs) import-flake;
+
+  # XXX(@fricklerhandwerk): this atrocity is required to splice in a foreign Nixpkgs via flake-parts
+  # XXX - this is just importing a flake
+  nixpkgs = import-flake { src = sources.nixpkgs; };
+
+  # XXX - this overrides the inputs attached to `self`
+  inputs' = self.inputs // {
+    nixpkgs = nixpkgs;
+  };
+  self' = self // {
+    inputs = inputs';
+  };
+
+  flake-parts-lib = import "${sources.flake-parts}/lib.nix" { inherit (nixpkgs) lib; };
+in
+
+flakeModule:
+
+flake-parts-lib.mkFlake
+  {
+    # XXX - finally we override the overall set of `inputs` -- we need both:
+    #       `flake-parts obtains `nixpkgs` from `self.inputs` and not from `inputs`.
+    inputs = inputs // {
+      inherit nixpkgs;
+    };
+    self = self';
+    specialArgs = {
+      inherit sources;
+    };
+  }
+  {
+    systems = [
+      "x86_64-linux"
+      "aarch64-linux"
+      "x86_64-darwin"
+      "aarch64-darwin"
+    ];
+    imports = [ flakeModule ];
+  }